The ability to control neural functions at widely different temperatures presents significant physiological and evolutionary challenges that have been overcome by many organisms. The major hurdle in temperature driven adaptations is the need to compensate for differences in energetic and kinetic properties of components intrinsic to molecular and cellular processes. While it is relatively easy to adaptively change the relative amounts of intrinsic components expressed in cells, it is far more difficult to scale controls for cells that have different intrinsic components and properties. The central hypothesis driving this research is that the adaptive value of temperature induced changes in a neural circuit is limited by the capacities of available control mechanisms. The pyloric central pattern generator (CPG) in the stomatogastric nervous system (STNS) of spiny lobsters produces rhythmic bursts of action potentials in motor neurons controlling food processing and, as such, is essential to survival. Preliminary studies indicate that Caribbean spiny lobsters, Panulirus argus, when maintained at 28 +/- 3 degrees C or 15 +/- 2 degrees C, produce apparently functional reconfigurations of the pyloric CPG. The proposed research will investigate the ability of animals to change bursting properties of pyloric cells and to modify controls for each reconfigured pyloric CPG: The research plan will: 1) Describe in detail the consequences of temperature acclimation on the pyloric CPG. 2) Quantify changes in synaptic strengths between interacting cells of the pyloric CPG as a function of acclimation history. 3) Determine the effects of acclimation and assay temperatures on known controls of the CPG. If the central hypothesis is correct, temperature changes in intrinsic bursting properties will necessitate a reconfiguration of control elements at each acclimation temperature. By the conclusion of these three sets of experiments, we will be better able to describe temperature effects on critical cycle parameters of the pyloric CPG in terms of acclimation history, function energetics and membrane lipids, intrinsic bursting properties, synaptic strengths, and the minimal neuromodulatory requirements needed to control those cycle parameters.